TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
1
XRT73L04 4-Channel DS3/E3/STS-1 LIU Power Conditioning
Requirements
1.0 OVERVIEW
XRT73L04 is a 4-Channel DS3/E3/STS-1 Transceiver (Line Interface Unit) that is
designed for use in multi-standard Networking and Transmission Systems.
The XRT73L04 device is a mixed signal device that supports the transmission and
reception of data at the DS3, E3 and STS-1 rates. Hence, this chip handles both digital
input and output signals (which switch at very fast rate and generate a lot of electrical and
radio frequency noise). Additionally, this chip also consists of four independent sensitive
analog receivers. As a consequence, the user must be careful in how to handle the VDD
and GND pins, in order to ensure good performance of the XRT73L04 device.
In particular, the user’s PCB layout and handling of the VDD and GND signals must
accomplish the following:
1. It must provide good isolation between the Transmit and Receive signals.
2. It must provide good isolation between Analog and Digital signals.
3. It must provide good isolation between each of the four (4) Channels within the
LIU IC
4. It must provide good isolation between signals from other components on the
board.
In many networking or transmission systems the source of power is a DC-DC converter,
which uses a switching converter to transform a -48VDC input to a +3.3VDC output. The
switching converter typically uses a switching frequency from 20KHz to 1MHz and the
3.3VDC power normally carries a significant amount of ‘ripple’ noise at this switching
frequency. This ripple noise can adversely affect performance of analog circuits in the
mixed signal devices (XRT73L04 and similar).
This application note presents some guidelines on how to layout and filter the VDD and
GND signals that are fed to the XRT73L04 device.
2.0 XRT73L04 ‘GND’ PINS
Tie all XRT73L04 ‘GND’ pins (pin numbers 6, 15, 18, 19, 22, 31, 49, 50, 56, 62, 63, 81,
89, 92, 100, 109, 112, 118, 124, 129 and 132) to the system ground plane. In case there
are separate analog and digital ground planes are available, tie all ‘GND’ pins to the
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
2
analog ground. Do not insert any impedance (an inductor or ferrite bead) between analog
and digital ground pins of XRT73L04.
3.0 XRT 73L04 ‘POWER’ PINS
The XRT73L04 device has 17 power supply pins. Pins 78, 86, 95, and 103 are the
receive analog section power supply pins. Pins 4, 10, 13, 24, 27, 33, 47 and 134 are the
transmit analog section power supply pins. Finally, pins 51, 58, 122 and 128 are digital
power supplies. The receive analog power supply pins (pins 78, 86, 95 and 103) are the
most critical as they power the four (4) clock recovery phase-lock-loops and therefore
power to these pins should be as clean as possible.
It is also desirable to keep the transmit power supply noise isolated from the receive
power supply. Further, it is also desirable to keep the individual channels (within a given
XRT73L04 device) isolated from each other. Finally, if multiple XRT73L04 devices are
used in a system it is further desirable to keep their power isolated (from each other) in
order to minimize cross-talk.
The attached schematic (Figure 1) illustrates Exar’s recommendations on how to connect
the Analog and Digital VDD pins (of a single XRT73L04 device) to a 3.3V Power
Supply. Exar’s approach recommends the use of two-stage LC filtering.
3.1 STAGE 1 – A LARGE LC FILTER (consisting of L1 and C1)
This particular LC filter consists of a 15uH inductor and a 33uF capacitor. The purpose
of this LC filter is to eliminate much of the “DC-to-DC Converter-induced” low
frequency ripple, within the 3.3V power supply line, prior to being routed to any of the
VDD pins of the XRT73L04 device.
NOTES ABOUT THIS LC FILTER:
1. This LC filter should be placed close to the output of the DC-to-DC Converter.
2. Only one such LC filter is needed, per board (even in multi-channel applications).
However, multi-channel designs may have to use multiple instantiations of this
LC filter due to large voltage drops across the inductor (due to the increased
amount of current draw of multiple XRT73L04 devices and the dc resistance of
the inductor), or because of the maximum operating current limit of this inductor
as well.
3. This LC filter may not be necessary if the 3.3V Power Supply is already filtered
elsewhere in the system.
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
3
COMPONENT SELECTION FOR L1 AND C1
The XRT73L04 device draws about 470mA of current. We recommend that the user
select a High Current Inductor, that has a small enough DC resistance such that the
voltage drop across the inductor will not exceed 50mV. Therefore, the user should select
a 15uH Inductor that has a DC resistance of less than 0.106Ω.
An example of an acceptable inductor for L1 is the 4922-15L from API-Delevan. This
particular inductor has a maximum dc resistance of 0.089Ω, and has a maximum current
rating of 2.11A. Contact information for API-Delevan is presented in Appendix A, at the
end of this Applications Note.
The capacitor, C1, should be a 33uF 10V Tantalum capacitor, which is supplied by
various manufacturers. Digikey PCT2336CT-ND or equivalent would be acceptable.
3.2 STAGE 2 – SMALLER LC FILTERING FOR RECEIVE AND
TRANSMIT ANALOG VDD PINS
After the Power Supply signal passes through the large LC filter (consisting of L1 and
C1), it should then be routed to nine different points, in parallel (in order to support each
of the four channels).
• Directly to the Digital VDD pins of the XRT73L04 device.
• To an LC filter (consisting of L2 and C2), prior to being routed to the Receive Analog
VDD pin of Channel 0 (pin 78).
• To an LC filter (consisting of L3 and C3), prior to being routed to the Transmit Analog
VDD pins of Channel 0 (pins 33 and 47).
• To an LC filter (consisting of L4 and C4), prior to being routed to the Receive Analog
VDD pin of Channel 1 (pin 86).
• To an LC filter (consisting of L5 and C5), prior to being routed to the Transmit Analog
VDD pins of Channel 1 (pins 24 and 27).
• To an LC filter (consisting of L6 and C6), prior to being routed to the Receive Analog
VDD pin of Channel 2 (pin 103).
• To an LC filter (consisting of L7 and C7), prior to being routed to the Transmit Analog
VDD pins of Channel 2 (pins 4 and 134).
• To an LC filter (consisting of L8 and C8), prior to being routed to the Receive Analog
VDD pin of Channel 3 (pin 95).
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
4
• To an LC filter (consisting of L9 and C9), prior to being routed to the Transmit Analog
VDD pins of Channel 3 (pins 13 and 10).
The purpose of this LC filter is three-fold:
1. To provide some isolation and filtering between the Digital VDD line and the
Analog VDD lines.
2. To provide some isolation (and reduce cross-talk) between the Transmit and
Receive Analog VDD lines.
3. To provide some isolation (and reduce cross-talk) between each of the four
channels within the XRT73L04 device.
NOTE: In contrast to the LC filter (consisting of Inductor L1 and Capacitor C1), these
LC filters must not be shared with other Channels or LIU Devices.
COMPONENT SELECTION FOR L2 – L9 AND C2 – C9
As mentioned above, each of the LC filter (consisting of Inductors L2 through L9 and
capacitors C2 through C9) are used to filter and isolate the power supply line, going to
each of the Receive Analog VDD pins and the Transmit Analog VDD pins. Each of
these inductors should be of value 6.8uH, and each of these capacitors should be of value
2.2uF.
The current consumption (via each of the Power Supply pins, of the XRT73L04 device)
is presented below in Table 1.
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
5
Table 1, The Current Consumption via each of the XRT73L04 Power Supply Pins
Pin Number Description Amount of Current
Measurements for Channel 0
33 Transmit Analog VDD – Channel 0 49.5mA
47 Transmit Analog VDD – Channel 0 4.22mA
58 Receive Digital VDD – Channel 0 16.1mA
78 Receive Analog VDD – Channel 0 48.6mA
Total Current Consumption – Channel 0 118.42mA
Measurements for Channel 1
24 Transmit Analog VDD – Channel 1 51.2mA
27 Transmit Analog VDD – Channel 1 6.7mA
51 Receive Digital VDD – Channel 1 16.15mA
86 Receive Analog VDD – Channel 1 49.2mA
Total Current Consumption – Channel 1 123.25mA
Measurements for Channel 2
4 Transmit Analog VDD – Channel 2 42.7mA
134 Transmit Analog VDD – Channel 2 4.5mA
122 Receive Digital VDD – Channel 2 16.28mA
103 Receive Analog VDD – Channel 2 48.3mA
Total Current Consumption – Channel 2 111.78mA
Measurements for Channel 3
13 Transmit Analog VDD – Channel 3 43.1mA
10 Transmit Analog VDD – Channel 3 4.15mA
128 Receive Digital VDD – Channel 3 16.11mA
95 Receive Analog VDD – Channel 3 49.7mA
Total Current Consumption – Channel 3 110.06mA
130 EXVDD 2.77mA
Total Current Consumption – XRT73L04 Device 466.28mA
For inductors L2 through L9, the user should select as large a value as the selected size
(0805, 1210 or 1812 etc.) will allow while keeping the DC resistance of each inductor to
less than 2 ohms. The goal is to keep the power supply voltage (at the VDD pins of the
XRT73L04 device) above 3.135 volts.
An example of an acceptable inductor would be the 1210-682J or the S1210-682K (each
of size 1210) from API-Delevan. The 1210-682J inductor is spec’d to have a maximum
dc resistance of 1.8ohms. Additionally, the 1210-682J inductor has a maximum current
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
6
rating of 321mA. The S1210-682K inductor is spec’d to have a maximum dc resistance
of 1.5ohms. Further, the S1210-682K has a maximum current rating of 372mA.
3.3 THE ZENER DIODE
It is strongly recommended that a 3.6V 400mW Zener Diode be connected from the
+3.3V supply to power GND to suppress power supply transients in case of excessive
charge injection into the Ground plane. These transients can occur while connecting the
remote terminal or test equipment to the board via coaxial cable. Such transients can
expose integrated circuit devices to momentary ‘reverse’ polarity or excessive (7V to
10V) power supply voltages. Most voltage regulators are too slow to respond to such
transient conditions.
NOTE: This zener diode is also useful for suppressing peak overshoots and ringing (in
the power supply line) following a rapid ramp in the power supply voltage, due to events
such as “hot-swapping”, etc.
An example of an acceptable 3.6V zener diode would be the 1N5914, which is available
from various suppliers.
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
7
3.4 DECOUPLING CAPACITORS
We strongly recommend that the user provide de-coupling capacitors for each VDD pin
of the XRT73L04 device (Analog as well as Digital). The placement and routing of these
decoupling capacitors must be such to minimize the trace length (and in-turn, inductance)
between the capacitor and the corresponding VDD pin, and the capacitor and the
corresponding via (which connects to the GND plane).
Miscellaneous Notes
The component values shown for capacitors and inductors are to be used as guidelines
only. Use following guidelines for selecting components:
For decoupling capacitors use X7R for ceramic non-polar capacitors, solid-
tantalum for polar capacitors. Avoid Z5U and electrolytic capacitors.
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
8
4.0 THE BNC CONNECTOR SHIELD
As a general rule, we highly recommend that the customer either AC or DC couple the
BNC connector shield to Frame or Chassis Ground. In the schematic design, we
recommend that the customer AC couple the BNC connectors (on both the Transmit and
Receive Sides) to Frame GND. Further, we also recommend that the customer also
design in a Jumper, which permits installation personnel to DC couple the BNC
connector shield to Frame GND, when set.
Component selection for the for the Capacitor (used to AC couple the BNC Connector
Shield to GND)
The characteristics of a capacitor, to be used in this role are as follows.
• This capacitor must be rated for high voltages.
• This capacitor must impose minimum AC impedance to Frame GND.
Therefore, the optimum choice for such a capacitor would be a capacitor that has a very
high voltage rating and very large capacitance. The best capacitor that we could find that
has both of these characteristics is a 1000pF capacitor that has a working voltage of
2000V.
SOME ACCEPTABLE CAPACITORS for AC Coupling the BNC Connector to Frame
GND
Any of the following capacitors are suitable for this applicable. In all cases, these are
Ceramic, X7R, 1000pF, 2kV, 10% capacitors which come in a 1812 case size.
Manufacturer Part Number
AVX 1812GC102KA11A
AVX 1812GC102KAT2A
CALCHIP CHV1812N2K0102KXT
JARO CC1812XR102JN202ER
JARO CC1812XR102KN202ER
MURATA GRM43-2X7R102K2KVAL
JOHANSON 202S43W102KV4E
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
(3.3V)
Install Close to the
DC-to-DC Converter or
Switching Regulator
(3.6V)
POWER_CON_SCH 1.01
Power_Conditioning_Circuit
B
1 1Wednesday, April 04, 2001
Title
Size Document Number Rev
Date: Sheet of
RECEIVE ANALOG VDD - CHANNEL 0
TRANSMIT ANALOG VDD - CHANNEL 0
TRANSMIT ANALOG VDD - CHANNEL 1
RECEIVE ANALOG VDD - CHANNEL 1
RECEIVE ANALOG VDD - CHANNEL 2
DIGITAL VDD
RECEIVE ANALOG VDD - CHANNEL 3
TRANSMIT ANALOG VDD - CHANNEL 2
TRANSMIT ANALOG VDD - CHANNEL 3
VDD
L1
15uH
L2
6.8uH
L3
6.8uH
L4
6.8uH
L5
6.8uH
L6
6.8uH
L7
6.8uH
L8
6.8uH
L9
6.8uH
C1
33uF
C2
2.2uF
C3
2.2uF
C4
2.2uF
C5
2.2uF
C6
2.2uF
C7
2.2uF
C8
2.2uF
C9
2.2uF
D1
D1N5914
DVDD
RxAVDD_0
TxAVDD_0
RxAVDD_1
TxAVDD_1
RxAVDD_2
TxAVDD_2
RxAVDD_3
TxAVDD_3
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
NOTE: BNC Connector
Shield (on Transmit
Side) is sometimes AC
coupled to Frame
Ground.
(2kV)
(2kV)
TAN_046_CH_0 1.01
XRT73L04_CHANNEL_0_DESIGN
A
1 1Wednesday, April 04, 2001
Title
SizeDocument Number Rev
Date: Sheet of
C12
0.01uF
C13
0.1uF
C14
0.1uF
C15
0.01uF
JP8
JUMPER
1 2
C35
1000pF
C38
1000pF
U1
XRT73L04_Channel_0
44
46
33
48
31
50
81
80
79
78
82
75
76
77
16
111
52
71
70
69
65
64
129
130
66
62
58
59
60
61
74
131
42
41
40 32
34
47
36
3572
110
49
TxLEV0
TAOS0
TxAVDD0
DMO0
TxAGND0
AGND
RxAGND0
RTIP0
RRING0
RxAVDD0
REQEN0
LOSTHR
LLB0
RLB0
STS-1/DS3_Ch0
LOSMUTEN
HOST/HW
SDI
SCLK
CS
RLOL0
RLOS0
DGND
DVDD
EXCLK0
RxDGND0
RxDVDD0
RCLK0
RNEG0/LCV0
RPOS0
ICT
TxOFF
TCLK0
TPDATA0
TNDATA0 TRING0
TTIP0
TxAVDD0
MRING0
MTIP0SDO
REG_RESET
TxAGND0
T1
T3001
1 6
3 4
T2
T3001
16
34
JP3
JUMPER
1 2
J1
BNC
1
2
J2
BNC
1
2
R1
37.4
R2
37.4
R3
274
R4
274
R5
31.6
R6
31.6
R7
100
R8
4.7k
C10
0.1uF
C11
0.1uF
TxCLK_CH_0
TxDATA_CH_0
LIU_RESET*
LIU_CS*
SERIAL_CLOCK_IN
SERIAL_DATA_IN
Rx_LOS_CH_0
RxLOL_CH_0
TxFAIL_CH_0
RxCLK_CH_0
LCV_OUT_CH_0
RxDATA_CH_0
SERIAL_DATA_OUT
DVDD TxAVDD_0
RxAVDD_0
REF_CLOCK_0
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
NOTE: BNC Connector
Shield (on Transmit
Side) is sometimes AC
coupled to Frame
Ground.
(2kV)
(2kV)
TAN_046_CH_1 1.01
XRT73L04_CHANNEL_1_DESIGN
A
1 1Wednesday, April 04, 2001
Title
SizeDocument Number Rev
Date: Sheet of
C16
0.01uF
C17
0.1uF
C18
0.1uF
C19
0.1uF
C20
0.1uF
C34
1000pF
U2
XRT73L04_Channel_1
43
45
24
26
19
63
89
88
87
86
90
84
85
83
68
67
57
56
51
53
54
55
30
29
28 23
25
27
20
21
22
TxLEV1
TAOS1
TxAVDD1
DMO1
TxAGND1
AGND
RxAGND1
RTIP1
RRING1
RxAVDD1
REQEN1
LLB1
RLB1
STS-1/DS3_Ch1
RLOL1
RLOS1
EXCLK1
RxDGND1
RxDVDD1
RCLK1
RNEG1/LCV1
RPOS1
TCLK1
TPDATA1
TNDATA1 TRING1
TTIP1
TxAVDD1
MRING1
MTIP1
TxAGND1
C37
1000pF
T3
T3001
1 6
3 4
T4
T3001
16
34
J3
BNC
1
2
J4
BNC
1
2
R9
37.4
R10
37.4
R11
274
JP7
JUMPER
1 2
R12
274
R13
31.6
R14
31.6
R15
100
JP4
JUMPER
1 2
RxLOS_CH_1
RxLOL_CH_1
TxFAIL_CH_1
RxDATA_CH_1
LCV_OUT_CH_0
RxCLK_CH_1
TxCLK_CH_1
TxDATA_CH_1
DVDD TxAVDD_1
RxAVDD_1
REF_CLOCK_1
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
NOTE: BNC Connector
Shield (on Transmit
Side) is sometimes AC
coupled to Frame
Ground.
(2kV)
(2kV)
TAN_046_CH_2 1.01
XRT73L04_CHANNEL_2_DESIGN
A
1 1Wednesday, April 04, 2001
Title
SizeDocument Number Rev
Date: Sheet of
C23
0.1uF
C24
0.1uF
C25
0.01uF
JP5
JUMPER
1 2
C33
1000pF
JP6
JUMPER
1 2
C36
1000pF
U3
XRT73L04_Channel_2
137
135
4
133
6
109
100
101
102
103
99
105
104
106
116
117
115
118
122
121
120
119
139
140
141 5
3
134
1
2
132
108
TxLEV2
TAOS2
TxAVDD2
DMO2
TxAGND2
AGND
RxAGND2
RTIP2
RRING2
RxAVDD2
REQEN2
LLB2
RLB2
STS-1/DS3_Ch2
RLOL2
RLOS2
EXCLK2
RxDGND2
RxDVDD2
RCLK2
RNEG2/LCV2
RPOS2
TCLK2
TPDATA2
TNDATA2 TRING2
TTIP2
TxAVDD2
MRING2
MTIP2
TxAGND2
E3_Ch2
T5
T3001
1 6
3 4
T6
T3001
16
34
J5
BNC
1
2
J6
BNC
1
2
R16
37.4
R17
37.4
R18
274
R19
274
R20
31.6
R21
31.6
R22
100
C21
0.1uF
C22
0.1uF
RxDATA_CH_2
LCV_OUT_CH_2
RxCLK_CH_2
RxLOS_CH_2
RxLOL_CH_2
TxFAIL_CH_2
TxCLK_CH_2
TxDATA_CH_2
TxAVDD_2
RxAVDD_2
DVDD
REF_CLOCK_2
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
NOTE: BNC Connector
Shield (on Transmit
Side) is sometimes AC
coupled to Frame
Ground.
(2kV)
(2kV)
TAN_046_CH_3 1.01
XRT73L04_CHANNEL_3_DESIGN
A
1 1Wednesday, April 04, 2001
Title
SizeDocument Number Rev
Date: Sheet of
R23
37.4
R24
37.4
C32
1000pF
U5
XRT73L04_Channel_3
138
136
10
11
15
112
92
93
94
95
91
97
96
98
113
114
123
124
128
127
126
125
7
8
914
12
13
17
16
18
107
TxLEV3
TAOS3
TxAVDD3
DMO2
TxAGND3
AGND
RxAGND3
RTIP3
RRING3
RxAVDD3
REQEN3
LLB3
RLB3
STS-1/DS3_Ch3
RLOL3
RLOS3
EXCLK3
RxDGND3
RxDVDD3
RCLK3
RNEG3/LCV3
RPOS3
TCLK3
TPDATA3
TNDATA3 TRING3
TTIP3
TxAVDD3
MRING3
MTIP3
TxAGND3
E3_Ch3
R25
274
JP1
JUMPER
1 2
R26
274
R27
31.6
R28
31.6
R29
100
JP2
JUMPER
1 2
T7
T3001
1 6
3 4
T8
T3001
16
34
J7
BNC
1
2
J8
BNC
1
2
C26
0.01uF
C27
0.1uF
C28
0.1uF
C29
0.1uF
C31
1000pF
C30
0.1uF
TxCLK_CH_3
TxDATA_CH_3
RxDATA_CH_3
LCV_OUT_CH_3
RxCLK_CH_3
RxLOS_CH_3
RxLOL_CH_3
TxFAIL_CH_3
DVDD TxAVDD_3
RxAVDD_3
REF_CLOCK_3
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
9
APPENDIX A
CONTACT INFORMATION FOR API-DELEVAN:
Corporate Office
API Delevan
270 Quaker Road
East Aurora, NY 14052
Phone: 716-652-3600
FAX: 716-652-4814
email: apisales@delevan.com
website: www.delevan.com
TAN-046
Application Note - XRT73L04 4-Channel DS3/E3/STS-1
LIU IC Power Conditioning Requirements
May 23, 2001
Revision 1.03
10
APPENDIX B – REVISION CHANGE HISTORY
CHANGES FROM REVISION 1.00 TO 1. 01
1. Modified Schematic Design to include Jumpers JP5, JP6, JP7 and JP8.
2. Changed Capacitors C31, C32, C33, C34, C35, C36, C37 and C38 to 1000pF
(2kV) capacitors.
CHANGES FROM REVISION 1.01 TO 1. 02
1. Included recommendations on handling the BNC Connector shield (Section 4.0)
CHANGES FROM REVISION 1.02 TO 1. 03
1. Included a list of acceptable part numbers for capacitors that can be used to AC
couple the BNC Connector shield to Frame GND (Section 4.0).